Deleading of gasoline by irradiation



Application September 28, 1956 Serial No. 612,896

7 Claims. (Cl. 204-154) (Granted under Title 35, U. S. Code (1952), see. 266) No Drawing.

The invention described herein, if patented, may be manufactured and used by or for the Government for governmental purposes, without the payment to us of any royalty thereon.

This invention relates to a process of deleading gasoline by irradiation, and more particularly to precipitation of tetraethyllead from gasoline containing the same by irradiation with high energy electrons.

The vast majority of automotive gasoline now on the civilian market and in military supply channels contains a significant quantity of tetraethyllead to improve its antiknock performance. Such gasoline is usually referred to as leaded gasoline. If prepared in accordance with commercial and military specifications, the tetraethyllead does not spontaneously separate from the leaded gasoline.

For special applications, it is sometimes desirable to use unleaded gasoline, i. e., gasoline substantially free from tetraethyllead. Such special applications include, for instance, the operation of gasoline stoves, inasmuch as tetraethyllead is a poisonous compound and its deposit on food prepared on such stoves would constitute a health hazard. Therefore, in order to operate gasoline stoves for the preparation of food, it is necessary either to have access to a supply of unleaded gasoline or to remove tetraethyllead from leaded gasoline. It is possible to carry out the latter operation by various physical processes, e. g., centrifugation, or chemically by the addition to the leaded gasoline of compounds capable of precipitating tetraethyllead; however, these processes leave much to be desired with regard to speed, ease and certainty of performance.

We have found surprisingly that tetraethyllead is precipitated from leaded gasoline irradiated. with high energy electrons, e. g., high energy electrons being emitted by a high voltage electron accelerator of the Van de Graafi type. Van de Graatl electron accelerators are available in a number of types at various operating voltages and power outputs, beginning with 1,000,000 electron volts and watts (Type JD); other types have operating voltages and power outputs of 2,000,000 electron volts and 500 watts (Type AD), and 3,000,000 electron volts and 12,000 watts (Type FD). All of them are capable of delivering effective dosages of ionizing radiation to leaded gasoline for the practice of our invention. Efi'ective doses depend on the amount of tetraethyllead present in the leaded gasoline and on the permissible residual amount of tetraethyllead that may remain in the deleaded gasoline, without impairing its special use, e. g., in a gassoline stove. We have found that a dosage of about 10 megareps or more precipitates up to about 90% of the tetraethyllead contained in ordinary automotive leaded gasoline. The precipitated tetraethyllead, which is ordinarily in the form of a white powder, can be easily and speedily removed from the irradiated gasoline by conventional mechanicalmeans, e. g., by filtration.

The term megarep as used here to denote the dosage of high energy electrons, means one million (1,000,000) reps (roentgen equivalent physical units). One rep ice (roentgen equivalent physical unit) is the amount of radiation which causes one gram of air or tissue or other material to absorb 83 ergs of radiation energy. The desired dosage of irradiation is applied to the material to be irradiated by exposing it to a source of ionizing radiation, such as a Van de Graaff high voltage electron accelerator, for one or more passes; thus, if a dosage of 30 megareps is desired and the irradiation source is capable of administering 2 megareps in a single pass to the material being irradiated, 15 passes will result in the desired dosage of 30 megareps.

Inasmuch as gasoline is a volatile, inflammable liquid, certain precautions must be taken in exposing it to a source of high energy electrons. We have found that precipitation of tetraethyllead from leaded gasoline, in the form of lead compounds such as lead bromide and lead oxide, by irradiation can be safely effected by first enclosing the leaded gasoline in a container which is permeable to high energy electrons, e. g., in a plastic bag made of Mylar, a terephthalate polyester made by E. I. du Pont de Nemours & Co. In lieu of a bag, the leaded gasoline may also be enclosed in a tank having a window of high-energy-electron-transmissive material (e. g., a window of Mylar or other terephthalate polyester sheet material). Also, particularly if a high energy electron source other than a high voltage electron accelerator is used, e. g., an atomic reactor containing beta-ray-emissive fission material, the leaded gasoline can be transmitted through the reactor in a straight or coiled pipe of beta-raypermeable material (e. g., of Mylar), at a controlled rate of flow to permit the absorption of the desired dosage of beta-rays (high speed electrons); deposits of lead compounds which build up in such a pipe may be periodically removed therefrom by conventional means, e. g., flushing with an appropriate diluent. The term container, as used in the specification and claims, is thus intended to denote a variety of means for confining liquid gasoline, including but not limited to bags, tanks, pipes and the like.

The following specific example illustrates one of the various ways in which our invention of removing tetraethyllead from gasoline by irradiation may be carried into practice, but is not intended to limit our invention to the specific details set forth therein:

Example Automotive gasoline of the type used in U. S. Army combat vehicles and containing 2.12 cc. of tetraethyllead per gallon was enclosed in a Mylar bag and irradiated by a Van de Graaff high voltage electron accelerator for fifteen (15) passes at adosage of 2 megareps per pass, or a total dosage of 30 megareps. A white precipitate formed at the bottom of the bag. The gasoline was decanted through a filter of sufiicient fineness to retain the white powder precipitate, and was then analyzed for tetraethyllead. The residue of tetraethyllead remaining in the treated gasoline was .26 cc. per gallon, or 88% less than its original tetraethyllead content. This gasoline is safe for cooking of food on a gasoline stove.

Having thus described our process and an illustrative example for carrying the same into practice, it will be understood that we wish to include within the scope of our invention any changes and modifications which will occur to persons skilled in the art without departing from the spirit of our invention, and to this end we define our invention by the appended claims.

We claim:

1. The process of precipitating tetraethyllead from gasoline containing tetraethyllead, comprising irradiating said gasoline with high energy electrons at a dosage of at least about 10 megareps, said electrons emanating from an electron accelerator of at least about 1,000,000 electron into material which is precipitable" in said gasoline, and" separating the precipitated material by filtration.

2. Process of removing tetraethyllead from gasoline containing material comprising irradiating said gasoline with high energy electrons at a dosage of at least about 30 megareps, said electrons emanating from an electron accelerator of at least about 1,000,000 electron'volts' capacity, whereby said tetraethyllead is decomposed into material which is precipitable in said gasoline, and separating'the precipitated lead compounds by filtration.

3. Process of precipitating tetraethyllead from gasoline containing tetraethyllead, comprising irradiating said gas oline with high energy electrons at a dosage of at least about 10 megareps emanating from an electron accelerator of at least about 1,000,000 electron volts capacity, whereby said tetraethyllead is decomposed into material which is precipitable in said gasoline, and separting the precipitated material.

4. Process according to claim 3, wherein said dosage is about 30 megareps.

5. Process according to claim 3, wherein said gasoline is enclosed in a high-energy-electron-permeable container during irradiation. 6. Process according to claim 5, wherein said container comprises terephthalate polyester material.

7. Process according to claim 2, wherein said gasoline is enclosed in a high-energy-electron-permeable container during irradiation.

References Cited in the file of this patent UNITED STATES PATENTS Rifkin-et a1. Dec. 25, 1951 OTHER REFERENCES UNITED STATES PATENT OFFICE Certificate of Correction Patent No. 2,867,572 January 6, 1959 John F. German et 2L1.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 8, line 5, for material read -tetraethyllead-.

Signed and sealed this 28th day of April 1959.

Attest T. B. MORROW,

Attestz'ng Oyficer.

ROBERT C. WATSON, Commissioner of Patents.

UNITED STATES PATENT OFFICE Certificate of Correction Patent No. 2,867,572 January 6, 1959 John F. German et 2L1.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 8, line 5, for material read -tetraethyllead-.

Signed and sealed this 28th day of April 1959.

Attest T. B. MORROW,

Attestz'ng Oyficer.

ROBERT C. WATSON, Commissioner of Patents.

UNITED STATES PATENT OFFICE Certificate of Correction Patent No. 2,867 ,572 J anuary 6, 1959 John F. German et a1.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the vsaid Letters Patent should read as corrected below.

Column 3, line 5, for material read -tetraethyl1ead.

Signed and sealed this 28th day of April 1959.

[sEAL] Attest ROBERT C. WATSON,

T. B. MORROW, Attestz'ng Oyficer. Uommissz'oner of Patents. 

1. THE PROCESS OF PRECIPITATING TETRAETHYLLEAD FROM GASOLINE CONTAINING TETRAETHYLLEAD, COMPRISING IRRADIATING SAID GASOLINE WITH HIGH ENERGY ELECTRONS AT A DOSAGE OF AT LEAST ABOUT 10 MEGAREPS, SAID ELECTRONS EMANATING FROM AN ELECTRON ACCELERATOR OF AT LEAST ABOUT 1,000,000 ELECTRON VOLTS CAPACITY, WHEREBY SAID TETRAETHYLLEAD IS DECOMPOSED INTO MATERIAL WHICH IS PRECIPITABLE IN SAID GASOLINE, AND SEPARATING THE PRECIPITATED MATERIAL BY FILTRATION. 